Classification of ABS flame retardants

 ABS resin has impact resistance, heat resistance, low temperature resistance, chemical resistance, easy processing and good surface gloss and other properties, currently widely used in automobiles, electronics, electrical appliances, textiles, appliances and building materials and other fields, so the flame retardant requirements of ABS are getting higher and higher.

Classification of ABS flame retardantsl:

1.Halogen flame retardants

① Bromine flame retardants: halogenated flame retardants mainly refer to bromine flame retardants. Brominated flame retardants are divided into the following categories

(a) Polybrominated diphenyl ethers: polybrominated diphenyl ethers include octabromodiphenyl ethers and decabromodiphenyl ethers, which are flame retardants with high efficiency, low dosage, good mechanical properties and affordable prices. However, this type of flame retardant does not comply with the RoHS ban, is a non-environmentally friendly product, and is now banned.

(b) Decabromodiphenyl ethane (DBDPE) : Because it contains non-free bromine, it does not belong to the polybrominated diphenyl ethers, and does not produce polybrominated biphenyls and polybrominated diphenyl ethers and other substances prohibited by the RoHS ban when burned.

The cost of DBDPE is comparable to decabDE, and the safety evaluation shows that DBDPE is a low-toxicity, non-stimulating flame retardant, negative for many genetic genes in vivo, and the repeated dose toxicity is also very low, which can replace PBDE as a flame retardant for ABS.

In addition, antimony flame retardant is an important flame retardant synergist, can be used alone or combined, especially when used with halogen flame retardant can greatly improve the efficiency of halogen flame retardant, is an indispensable synergist in halogen flame retardant. Its main varieties are Sb2O3, Sb2O5 and sodium antimonate (NaSbO3 •14H2O).

(c) Brominated epoxy resin: Brominated epoxy resin refers to the epoxy resin synthesized by tetrabromobisphenol A, which has excellent melting fluidity, high flame retardant efficiency, excellent thermal stability and light stability, and has good physical and mechanical properties, and is an ideal ABS flame retardant.

② Chlorinated polyethylene (CPE) flame retardant: CPE appearance is white powder, non-toxic, soluble in aromatic hydrocarbons and halogenated hydrocarbons, insoluble in aliphatic hydrocarbons, decomposition above 170℃, release hydrogen chloride gas.

Because the CPE molecular structure does not contain unsaturated double bonds and access to chlorine-containing groups, and chlorine atoms are randomly distributed along the polyethylene chain, it has a stable chemical structure, excellent heat aging resistance, cold resistance, weather resistance, chemical resistance, ozone resistance and electrical insulation.

As an elastomer polymer, CPE has good compatibility with a variety of polymers, and can be used as a modifier of ABS, PVC, PP, PE, PS, etc.

At the same time, because CPE contains halogen, flame retardant, can be used as a second flame retardant, and the price of CPE is lower than ABS, so CPE is an ideal choice for flame retardant ABS modification.

The synergistic flame retardant effect of CPE and Sb2O3: When CPE is added to the material of ABS and composite flame retardant DBDPESb2O3, the oxygen index of the composite material will increase, and the heat release rate, effective combustion heat and mass loss rate will decrease, indicating that CPE has a flame retardant effect and can be used as a second flame retardant.

After the addition of CPE, the impact strength of the composite is greatly increased, indicating that there is a synergistic effect between CPE and Sb2O3. In addition, after adding CPESb2O3, the smoke generation rate of the composite can be significantly reduced, indicating that CPESb2O3 also has a good smoke suppression effect on ABS.

③ halogen-free flame retardants

Aluminum hydroxide and magnesium hydroxide: Aluminum hydroxide and magnesium hydroxide are two common inorganic filler-type flame retardants, which are characterized by halogen-free, non-toxic, smoke-suppressing and inexpensive.

Its flame retardant mechanism is basically the same, all are based on the condensed phase flame retardant mechanism (that is, aluminum hydroxide forms a condensed phase on the ABS surface at high temperature, which insulates the air, prevents heat transfer, and reduces the release of combustible gas.

The formed carbon layer can block the feedback of combustion heat to the unburned part and the diffusion and combustion of decomposition products to the flame zone, play a role of heat insulation and mass insulation, can effectively reduce the heat release rate of the material, delay the combustion of the material) and cooling mechanism (that is, the flame retardant occurs endothermic dehydration, phase transition, decomposition or other endothermic reactions, reduce the temperature of the polymer surface and the combustion zone. Prevents thermal degradation, thereby reducing the amount of volatilization of combustible gases, and ultimately destroying the conditions that maintain the continuous combustion of the polymer).

However, the amount of addition alone is large, and the mechanical properties of the resin are greatly changed, so these two flame retardants are generally not commonly used as main flame retardants.

Coated red phosphorus: coated red phosphorus only contains the flame retardant element phosphorus, and its flame retardant efficiency is higher than other phosphorus-containing flame retardants. Its flame retardant mechanism is mainly condensed phase flame retardant, that is, red phosphorus coated at high temperature forms a condensed phase on the ABS surface, isolating the air, preventing heat transfer, reducing the amount of flammable gas release, so as to achieve the purpose of flame retardant.

However, the effect of coated red phosphorus flame retardant ABS is not obvious when used alone, and better flame retardant effect can be obtained when combined with other synergists. It is found that when the amount of coated red phosphorus is 9% and the amount of aluminum hydroxide is 20%, the synergistic and environmentally friendly flame retardant ABS with good mechanical and flame retardant properties can be obtained.

④Phosphorus and nitrogen composite flame retardants: nitrogenous flame retardants are mainly flame retarded by forming non-combustible gases such as nitrogen during decomposition, diluting and diluting combustible gases or covering the surface of the material. Its common are melamine, melamine cyanurate (MCA), melamine pyrophosphate and so on.

Intumescent flame retardants with phosphorus and nitrogen as the main components become halogen-free flame retardants in ABS. When phosphorus compounds are added to nitrogen, phosphorus-nitrogen flame retardants can be formed. Because nitrogen compounds release N2, CO2, NH3, H2O and other gases after heating, these non-combustible gases block the supply of oxygen, achieving the purpose of flame retardancy and synergism.